Answer: 9.76%
Step-by-step explanation:
The cost today of $29,000 is the future value of the cost 20 years ago with the growth rate in question. It can therefore be solved by the future value formula;
29,000 = 4,500 * ( 1 + r/100)²⁰
( 1 + r/100)²⁰ = 29,000/4,500
1 + r/100 = ²⁰√29,000/4,500
1 + r/100 = 1.0976
r = 9.76%